In general, a rotatable body rotated by a motor via a shaft is used in various technical fields. The rotatable body and the shaft may be connected by a connector to integrally rotate without rumbling. In image forming apparatuses, rotatable bodies are used in driving mechanisms, for example, for a photoreceptor on which a toner image is formed, an intermediate transfer belt to which the toner image is transferred from the photoreceptor, etc.
FIG. 1 illustrates an example related art connector for connecting a shaft and a rotatable body. In FIG. 1, a joint 360 that is a rotatable body having an attachment hole 440 is connected to a shaft 340 fitted into the attachment hole 440 with a pin 450 fixed on the shaft 340 and a screw 510 including a head 520.
The pin 450 penetrates the shaft 340 and fits into an engaging groove 460 formed on the joint 360. The screw 510 is screwed into a screw hole 500 provided on an end face 490 of the shaft 340. A bearing 320 fits around the shaft 340. The joint 360 engages with a partner joint 410. The head 520 is pressed against an inner surface 530 of the joint 360. Accordingly, a surface 154 of the joint 360 facing the bearing 320 is pressed to the bearing 320.
FIG. 2A illustrates a B-B cross-section of FIG. 1. As illustrated in FIG. 2A, the engaging groove 460 includes side surfaces 470 and 480. When the shaft 340 is pressed to fit the attachment hole 440 of the joint 360, tiny gaps G are required between the pin 450 and each of the side surfaces 470 and 480 of the engaging groove to fit the pin 450 into the engaging groove 460.
When the shaft 340 rotates in FIG. 1, a frictional force is generated between the surface 154 of the joint 360 and the surface of the bearing 320. Therefore, rumbling (relative rotation) of the joint 360 with respect to the shaft 340 is reduced. However, the rotation of the shaft 340 may not be transmitted to the joint 360 for a brief moment due to the gaps G. Therefore, the joint 360 may not rotate in an integrated manner.
For example, when a photoreceptor that is rotated in a direction and a reverse direction thereto is connected to the shaft 340 via the joint 360 and the partner joint 410, the rumbling may become a problem. When image forming is started and the shaft 340 rotates, the rotation is transmitted to the photoreceptor via the joint 360 and the partner joint 410. As a result, a significant external force is applied to the photoreceptor.
Therefore, the joint 360 rotates relatively to the shaft 340 pressed into the attachment hole 440 for a distance corresponding to the gap G as shown in FIG. 2B. A first end of the pin 450 presses the side surface 470 and a second end of the pin 450 presses the side surface 480. A toner image is formed on the photoreceptor in this state and transferred onto an intermediate transfer belt. If the photoreceptor is rotates in one direction only, the pin 450 stays at a similar position and the rumbling of the joint 360 may be insignificant.
However, when the photoreceptor is reversely rotated, the joint 360 rotates relatively to the shaft 340 for a distance corresponding to the gaps G as shown in FIG. 2C. The first end of the pin 450 presses the side surface 480 and the second end of the pin 450 presses the side surface 470. As described above, rumbling of the joint 360 occurs because the rotation of the shaft 340 is not immediately transmitted to the joint 360 due to the gaps G.
If the image forming apparatus is tandem type and includes a plurality of photoreceptors, the photoreceptors may rotate at different moments relatively to the respective shafts 340. This may cause displacement of colors when the toner images on the photoreceptors are superimposed one on another on the intermediate transfer belt.